Volume One 8. Indigenous Biodiversity Wetlands The term wetland covers habitats where the land is covered in or wetted by water for most (but not necessarily all) of the time. Wetlands occur in areas where surface water collects or where groundwater seeps to the surface. They include swamps, bogs, coastal wetlands, lakes and some river edges. Wetlands are highly productive environments that can support a diverse range of plants and animals (birds, fish, insects and micro-organisms). They support processes that provide environmental services such as water storage and flood control, nutrient removal, erosion control and water table maintenance. Wetland areas have always been highly valued by Māori as they provide a rich source of traditional resources like food (fish and birds), flax and medicinal plants. Wetlands therefore represent a significant part of Marlborough’s natural heritage. Between 1920 and 1980, most of New Zealand's wetlands were drained for pastoral land use. This has resulted in an approximately 85% reduction in wetland areas and many remaining wetlands are still under pressure from land development. Many remaining wetlands are small and their natural character and habitat quality have been degraded by partial drainage, damage by farm animals and weed invasion. Lowland wetlands have been worst affected and in some cases are still at risk. The systematic draining of Marlborough’s wetlands over the last 150 years has had a profound impact on aquatic ecosystems, especially in the lowland areas of the Wairau Plain. Less than one percent of the Wairau Plain wetlands that existed before Europeans arrived in New Zealand still exist. In addition, the taking of groundwater or surfacewater can affect the habitat and flow regimes of wetlands. Marine environments Marlborough supports a wide variety of marine habitats, ranging from exposed rocky shores to sheltered sandy bays. The coast is affected by a wide variety of physical and biological processes including tidal currents, wave energy, water clarity, substratum and temperature. Marlborough’s geographic location influences these processes and as a result, our marine environment is one of the most interesting of any coastal areas in New Zealand, supporting a high diversity of species. Furthermore, Marlborough is an important part of the migratory route for several large marine mammals, including humpback and southern right whales. Other marine mammals live in Marlborough’s marine environment, including the nationally endangered Hector’s dolphin, which resides in Cloudy-Clifford Bays and Queen Charlotte Sound. Species such as dusky dolphins and orca regularly visit the Marlborough Sounds, while bottlenose dolphins are found here during most of the year. Marlborough’s marine environment supports a significant diversity of sea birds, most of which rely on the area for breeding, raising young or for feeding. Of particular note is the king shag, which is endemic to the Marlborough Sounds. Tidal wetlands, although mostly small and widely spread throughout Marlborough, form an important network for mobile species of wetland bird. Larger estuaries do exist, including those at Whangarae (Croisilles Harbour), Havelock, Kaiuma and Wairau Lagoons. These larger estuaries provide habitat and feeding areas for a wide variety of fish, invertebrates and birds. The condition and state of marine biodiversity can be affected by land or water based activities. Adverse impacts can arise from sedimentation, contamination and habitat disturbance. Effects can be temporary, but in particular circumstances can result in permanent loss or damage. Long term or cumulative smaller scale, localised effects from impacts such as contamination and physical disturbance can also have significant effects on the functioning of marine systems. Many activities, such as recreational swimming, do not affect or have an impact on marine biodiversity; however, other activities, including shipping (especially large and/or fast ships), reclamations or other coastal structures, marine farming and physical disturbance from certain fishing techniques can affect marine biodiversity. 8 – 3